Since its first extraction by Banting and Best in 1921, insulin has been administered to countless thousands of diabetic patients with dramatic and life-saving effects. Not surprisingly, insulin has been intensively studied over the succeeding seventy years as a model peptide and elucidation of its crystallographic structure, peptide sequence, radio ligand assay and chemical synthesis represent major achievements in the history of molecular biology. Despite all of the work which has been done, the original method for self administration of insulin, namely subcutaneous injection, persists to this day and it is widely assumed it is this non-physiological route that results in the well known very poor control of blood glucose. It is also well known that when extracted insulins are injected hypoglycemia is readily produced by a small overdose, whereas when natural insulin delivery is restored to a diabetic patient, such as by pancreatic or Islet of Langerhans cell transplantation, hypoglycemia is not a problem. It appears, therefore, that while extracted insulins are very similar to natural insulins, they are not, in fact, the same. Indeed, over the years, the standard assay (mouse convulsion assay) to determine the potency of an extracted (pharmacological) insulin measures the amount of insulin necessary to induce rapid hypoglycemia in a typical normal animal whereas hypoglycemia is not produced at all with native (indogenous) insulin. By this assay, therefore, endogenous insulin could be said to be nonpotent.
The present inventor hypothesizes that the chemical extraction process commonly employed to obtain insulin from recombinant sources or from bovine or porcine pancreas denatures or degrades the native (indogenous) insulin or that the handling of the pharmacological insulin in some measure degrades the material. It is interesting to note that Banting and Best, in 1921, reported one water solubilized extract which normalized blood sugar in a diabetic dog but did not produce hypoglycemia and which was subsequently abandoned as unproductive, in favour of more vigorous chemical extractions with a more potent hypoglycemic action. Apparently Banting and Best did not appreciate the significance of their results which indicate to the present inventor that some subtle degradation of indogenous insulin occurs during chemical extraction in normal animals.
Following major studies into the human biochemical fuel cycle and many of the constituent substrate-hormonal interdependencies using a comprehensive metabolic simulator which included details of the energy cycles of carbohydrate-, protein-, and fat- derived fuel substrates, the inventor herein postulates that the chemical production of pharmacological insulin strips phosphate groups from the outer surfaces of the insulin molecule from residues widely known to be phosphorylatable and that phosphorylation of chemically extracted insulin is capable of producing an insulin which (a) will not invoke hypoglycemia in normal subjects (b) will reduce hyperglycemia in diabetic subjects but only to normal levels and (c) is not dose-response dependent.
Phosphorylation of amino acids, proteins and peptides including insulin is not novel. Attention is directed to U.S. Pat. No. 4,705,845 issued 10 November 1987, but such modified insulins retain about 85% of the bio-activity of the unphosphorylated starting material and hence induce hypoglycemia in diabetic and non-diabetic subjects. Clearly such phosphorylated materials contain a considerable amount of unreacted or de-graded material.